With the advantages such as high brightness, low heat, long service life, and being environmentally friendly and renewable, LEDs are known as the most promising new generation of green light sources in the 21st century. At present, the theoretical service life of the LED can be over 100,000 hours. However, during actual application, limited by many factors such as chip failure package failure, thermal overstress failure, electrical overstress failure, and/or assembly failure, especially limited by the package failure, the LED prematurely encounters luminous decay or loss of luminous efficacy, thus hindering development of the LED to be a novel energy-saving light source. To solve these problems, many scholars in the field have carried out related researches, and have proposed some improvement measures to enhance luminous efficacy and actual service life of the LED. For example, flip-chip LED packaging is developed in recent years. Compared with conventional LED upright packaging, this flip-chip manner has such advantages as high luminous efficacy, high reliability, and easy integration. This manner also greatly saves packaging materials. For example, materials such as a gold wire, die bonding glue, and a support that are used in the conventional LED upright packaging are no longer needed. Further, this manner greatly simplifies a packaging process method. For example, die bonding, wire soldering, and even light splitting in the conventional LED upright packaging are no longer needed. In this way, the LED flip-chip packaging is increasingly widely applied. However, it should also be noted that, the existing flip-chip LED packaging technologies mostly bond a photoconverter made of an organic silicone resin to a flip chip LED using a casting process, a screen printing process, an upper and lower flat plate molding process, a single roller pressing process, and the like. These processes and matched packaging equipment cannot desirably solve flaws such as pores and unequal thickness of the photoconverter made of the organic silicone resin, thus causing a low yield of the LEDs packaged by using a photoconverter. In addition, due to low production efficiency, the high product costs cannot be reduced.
Chinese patent application NO. 201010204860.9 discloses a “flip-chip LED packaging method”, which includes steps of: (a) coating a surface of an LED chip with a photoconverter through screen printing, and baking the photoconverter to cure the photoconverter; (b) fixing the LED chip on a chip substrate, such that electrodes of the LED chip and electrodes of the chip substrate are bonded; (c) fixing the LED chip and the chip substrate to the bottom of a reflector cup on a support; (d) separately connecting positive and negative electrodes of the fixed chip substrate to positive and negative electrodes of the support by using wires; (e) placing a sealing mold or lens cover on the support on which the LED chip and the chip substrate are fixed, and filling the sealing mold or lens cover with silica gel; and (f) baking the whole structure to cure it. This method uses the screen printing process to enhance uniformity of coating thickness of the photoconverter and enhance distribution uniformity of fluorescent powder particles, so as to improve the yield. However, there exist the following obvious defects: First, after the surface of the LED chip is coated with the photoconverter made of the organic silicone resin through a screen printing process, due to thermal overstress in a subsequent baking and curing procedure, pores still occur in part of the photoconverter coating and the coated surface of the LED chip, thus forming sags and crests. Secondly, after the sealing mode or lens cover is filled with the silica gel and packaged together with the photoconverter-coated LED chip, due to thermal overstress in the subsequent procedure of baking and curing the whole structure, pores still occur in part of the silica gel layer on the sealing mold or lens cover, thus forming sags and crests. Because the thermal overstress impact on the LED chip cannot be resolved in the packaging procedure, LED luminous efficacy is reduced inevitably. Thirdly, an intelligent control system is not equipped to control the whole LED chip packaging process, which directly affects improvement of the yield.
Chinese patent application NO. 201310270747.4 discloses an “LED coated with photoconverter layer, manufacturing method for same, and LED device”. This solution includes: an LED configuration stage, in which an LED is configured on a surface of a support chip in a through-thickness direction; a layer configuration stage, in which a photoconverter layer is configured on a surface of the support chip in the through-thickness direction in the same manner as LED configuration, the photoconverter layer being formed by active energy ray cured resin which is cured by irradiation with an active energy ray and a fluorescent resin composition of the photoconverter; a curing stage, in which the photoconverter layer is irradiated with an active energy ray to cure the photoconverter layer; a cutting stage, in which the photoconverter layer is cut corresponding to the LED, to obtain an LED coated with the photoconverter layer; and an LED separation stage, in which the LED coated with the photoconverter layer is separated from the support chip after the cutting process. This method aims to offer a solution to uniform configuration of photoconverters around the LED to avoid damage, thus obtaining an LED coated with a photoconverter layer, and an LED device having the LED coated with the photoconverter layer. However, there exist the following obvious defects: First, in a curing procedure of the fluorescent resin composition of the photoconverter, due to thermal overstress, pores still occur in part of the photoconverter surface layer, thus forming sags and crests. Secondly, the LED coated with the photoconverter layer is still affected by the thermal overstress, causing a decrease in luminous efficacy of the LED in use. Thirdly, the stages of the whole packaging process are complicated, causing low production efficiency of LED packages. Fourthly, an upper and lower flat plate molding process may cause displacement of a flip chip, and there is no intelligent control system for accurate control, thus inevitably reducing the yield.
Chinese patent application NO. 201380027218.X discloses a “resin sheet laminate, and manufacturing method for semiconductor light-emitting element using same”. In this solution, the resin sheet laminate is formed by disposing a fluorophor-containing resin layer on a substrate, where the fluorophor-containing resin layer has multiple regions, the substrate has a lengthwise direction and a transverse direction, and the multiple regions are arranged along the lengthwise direction repeatedly to form columns. By using the resin sheet laminate, this solution aims to enhance uniformity of color and brightness of a semiconductor light-emitting element to which the fluorophor-containing resin layer is attached, and make it easy to manufacture and free to design the element. However, there exist the following obvious defects: First, the used fluorescent resin sheet is a cured fluorescent resin sheet, and therefore, possible residual pores, sags and crests, or other flaws produced during processing cannot be effectively eliminated. Secondly, in a bonding stage, a pressure is exerted by a pressurizing tool from a side of the semiconductor light-emitting element, which may damage the semiconductor light-emitting element. Thirdly, in the bonding stage using an adhesive in the fluorophor-containing resin layer, it is difficult to eliminate residuals from the semiconductor light-emitting element after bonding, and pores easily occur in the bonding procedure, thus reducing the yield; in addition, existence of the bonding layer reduces light emission efficiency of the LED element. Fourthly, the substrate under the fluorescent resin sheet bonded to the light emitting surface of the semiconductor light-emitting element is not removed, which directly affects luminous efficacy of the semiconductor light-emitting element. Fifthly, the multiple regions of the fluorophor-containing resin layer are arranged in the lengthwise direction repeatedly to form columns, but actually it is complex to arrange the multiple regions of the fluorophor-containing resin layer in such a manner, thus affecting the packaging efficiency of the whole element. An error in arrangement positions of the multiple regions directly affects the precision of subsequent bonding with the light-emitting element. If the multiple regions cannot be rendered uniform in size and thickness, a severe problem of product inconsistency may emerge.
To sum up, how to overcome the defects in the prior art has become one of major difficulties to be solved in the technical field of LED packaging using a photoconverter.